1. FIELD OF THE INVENTION
The present invention concerns a method of manufacturing a liquid crystal display element.
2. DISCUSSION OF BACKGROUND
Liquid crystal displays have been utilized generally in recent years for various domestic electric products, portable electronic calculators, watches, word processors, hand-held computers, portable TV sets, etc. while utilizing advantageous features of low power consumption, low voltage driving, etc.
In nematic liquid crystal of a structure put between a pair of substrates provided with electrodes, liquid crystal molecules are arranged in perpendicular to the surface of the substrates or arranged in a twisted state depending on voltage application conditions. A twisted nematic (TN) type liquid crystal display element for conducting display by putting liquid crystal between a pair of polarization plates has generally been employed by utilizing such a difference in the optical property.
On the other hand, it has also been proposed in recent years to put a liquid, crystal and polymer composite between a pair of substrates provided with electrodes by using the liquid crystal and polymer composite in which liquid crystal is dispersed and maintained in a resin matrix.
In this case, nematic liquid crystal is dispersed and held in the resin matrix in the liquid crystal-polymer composite, so that the refractive index of the resin matrix substantially agrees with the ordinary refractive index (n.sub.0) of liquid crystal used.
Since liquid crystal is oriented substantially in parallel with the wall surface to which it is dispersed in the usual state, i.e., in a state not applied with a voltage in the liquid crystal and polymer composite, the refractive index is different from that of the resin matrix and light is scattered at the interface to provide a scattered (opaque) appearance.
When a voltage is applied between a pair of substrates provided with electrodes, since the liquid crystal turn-up substantially in perpendicular to the surface of the electrodes, the refractive index of the resin matrix substantially agrees with the ordinary refractive index of the liquid crystal used to provide a light transparent state.
Various kinds of displays are thus enabled by utilizing the optical difference.
A liquid crystal display element using such a liquid crystal and polymer composite has a merit capable of easily preparing a large area display body and is expected for light controlling application use. Further, since polarization plates are no more required, it also has a merit capable of obtaining bright display.
In a liquid crystal display element using such a liquid crystal and polymer composite, a mixture of nematic liquid crystal and curable compound is usually used, which is supplied to one of the substrates provided with an electrode and the curing compound is cured before or after overlaying the other of the substrates. Thus, the nematic liquid crystal is dispersed and held in the resin matrix.
As a specific example, there is a manufacturing method of mixing nematic liquid crystal with an aqueous solution of polyvinyl alcohol, casting to supply a mixture in which the nematic liquid crystal is dispersed in the aqueous solution of polyvinyl alcohol on one of the substrates equipped with an electrode, evaporizing water and curing polyvinyl alcohol, thereby forming a liquid crystal and polymer composite in which the nematic liquid crystal is dispersed in the polyvinyl alcohol matrix and overlaying the other of the substrates thereover, to obtain a liquid crystal display element.
Further, there is also a method of manufacturing a liquid crystal display element by mixing nematic liquid crystal and light curable acrylic resin material into a solution, casting to supply-the solution on one of the substrates provided with an electrode, laying the other of the substrates thereover, using the light curable acrylic resin material under the irradiation of light and forming a liquid crystal and polymer composite in which the nematic liquid crystal is dispersed in the acrylic resin.
In the case of a light controlling body using an entirely deposited electrode, such a manufacturing method has a merit of providing an extremely high productivity even for a liquid crystal display element having a large area.
However, in the case for the application use of a display element in which the aligning accuracy is important between upper and lower substrates, the foregoing manufacturing method involves a problem in the alignment can not be attained easily but often causes displacement.
In view of the above, there may be considered to use a manufacturing method as employed in conventional TN type liquid crystal display elements in which a cell is formed and liquid crystal is injected under a reduced pressure therein, but this involves a problem that desired characteristics of the liquid crystal display element can not be obtained easily by merely injecting the liquid crystal under the reduced pressure.